Drilling or service rigs employ pipe or tube casings when drilling an oil well. The pipes need to be delivered to, or removed from, the mouth of the drilling rig in succession. Rig floor heights are determined by various safety devices attached to the top of the oil well and require some means of getting pipe from the ground to vertical inside the derrick of a rig. Manual lifting and positioning of the pipe onto the mouth of the drilling rig is time consuming and requires enormous utilization of manpower. To overcome this difficulty, there have been machines and apparatuses known to exist in the prior art that at least partially automate the delivery of the pipe or tube casings onto the drilling or service rig. One such apparatus is disclosed in U.S. Pat. No. 4,235,566 granted to Beeman et.al., which discloses a pipe-conveying catwalk. The pipe-conveying catwalk has a ramp affixed to the floor of a drilling rig and a main frame that is ground supported adjacent to a pipe rack so that pipe can be conveyed between the rack and the derrick (or rig) floor. Pipe is rolled from the rack into a trough which forms part of a stinger. The stinger is nested within a boom and can be telescoped to extend longitudinally away from the boom. The boom is retracted into nested position within the main framework. One end of the boom is attached to the main frame by an extensible swing arm apparatus which elevates the outer end of the boom while the other end of the main frame is attached to the rig floor by a ramp which moves the other end of the boom from the nested position vertically upwards and towards the rig floor. A pipe is rolled from the pipe rack into the trough, the boom is elevated into an inclined position such that the stinger telescopes from the boom to position the box end of the pipe in overlying relationship respective to the derrick floor. Roughnecks can then pick the pipe vertically upward into the drilling rig and attach the pipe joint to the pipe string located in a borehole. When coming out of the hole, the opposite procedure is involved in order to transport the pipe from the rig floor back onto the pipe rack. The pipe conveying catwalk of Beeman's Patent is a permanent structure fixed to the rig floor. The pipe conveying is predominantly through a boom connected to the catwalk.
A US Patent Application bearing number 20100068006 filed in the name of Richard Littlewood discloses a catwalk for a drilling rig. The pipe handling catwalk includes a deck having an upper surface, a first end, an opposite end and a tubular support surface on the upper surface, the tubular support surface being elongate and extending between the first end and the opposite end. A deck guide including a wall extending up from the deck upper surface and drivable along tubular support surface of the deck is provided. A ramp is mounted on the deck adjacent its first end and positionable extending at an angle from the deck. A carrier is connected to the ramp to remain on the ramp and is moveable such that an end thereof can be lifted away from the ramp to reduce the inclination of the carrier relative to the angle of the ramp, the carrier including an upper surface and a tubular retaining surface thereon extending along the carrier substantially in line with the tubular support surface of the deck. Littlewood's application provides a two stage pipe handling catwalk. Further the apparatus has to be permanently fixed adjacent to the drilling rig. The inclination of the ramp with respect the deck is also fixed.
U.S. Pat. No. 4,684,314 assigned to Weatherford/Lamb Inc discloses a pipe handling apparatus. The pipe handling apparatus is adapted for transferring oil well pipe to and from a drilling rig. The apparatus includes a transportable chassis having tracks for supporting and guiding a reciprocable and rotatable table. A first scissors lift mounted to the table provides vertical motion to a platform to which is mounted a second scissors lift. The second scissors lift is designed to impart vertical and horizontal motion to a conveyor. The conveyor comprises three axially spaced endless belts for moving the pipe longitudinally to the conveyor takeoff point. Tapered spades protrude into the spaces during the pipe return operation to eject the pipe from the conveyor. The conveyor and platform are reciprocable with respect to the second and first scissors lifts, respectively. The chassis includes pivotable arms for raising a pipe to the top of the collapsed scissors lifts so that a pipe rolls onto the conveyor belts prior to lifting. The pipe handling apparatus according to Weatherford/Lamb's Patent is a conveyor based apparatus with two stage elevation of pipe. Although the patent provides a transportable chassis, the apparatus has to be fixed prior to operation.